Slushing oil



ins oils.

Patented Nov. 9,

"UN Iran ,STAT

sfPATENT OFFICE ,sLUsnmG on.

Elmer W. Cook, New York, N. 1L, and William Thomas, Jr., Stamford, Comm, assignors to American" Cyanamid Company, New Iiork, Ya

a corporation of Maine No Drawing. Application July 2', 1941, 4 Serial No. 409.315

(Cl. 106- 14) V Claims.

This invention relates to corrosion-preventing coating compositions of the typeknown as slushparedby adding to slushingpils of any desired type such as those outlined above certain dialkyl Slushing oils, .as generally known, consistof or semi-finished metal objects such as machinery,

machine tools, engines, gun barrels, sheet'steel, etc., particularly when fabricated of iron or steel, are to be stored or shipped over salt water or in tropical climates they. are generally treated with a heavy coating of a slushing oil to prevent cor-1- j rosion. Slushing oils are also employed to prevent corrosion of fine steel products such as razor blades which must be toucheclwiththe workmens hands during manufacture and inspecting operations.

Ordinary contain no corrosive substances land-as long as they remain on themetalgsurface and protectfit from contact with water,- acids, air and other gases which tend to promote corrosion. Unforslashing oils such as described are satisfactory fortheir intended purpose if they tunately, however, ordinary slushing oils do not adhere to metal 'surfaces as well as desired and are easily rubbed off during shipping and hendling. Various substances such as natural and synthetic resins have been added to slushingf oils with the intention of causing them to adhere more firmly to the metal surface. Thisipractice has obvious disadvantages especially when the oil is applied to some objects and later on when it is to be removed. 'Other suggestions have been made to increase the adherence of the-oil on the metal surfaces but in general the principal attempts have been'made to provide an oil which has the inherent qualities of adherence so much desired.

We have found that slushing 'oils may be prepared which retain the advantages of-slus hing oils heretofore employed and at the same time are of much greater effectiveness because of the great tenacity with which they adhere to metal surfaces and also because of other properties which will be presently described.) Our improved slashing oils ofthe present invention are prediphenol sulfide metal salts having the general formula in which R, R1, R2 and R: are alkyl radicals having 4 or more carbon atoms in each alkyl group and M is a metal. When M is a divalent 1 metal such as barium the formula may become I O O B-QSQR: 1 2

and when a polyvalentmetal such as aluminum or chromium is used the resulting salts are com plex in nature. The dialkyl phenol sulfide-of our invention may therefore be defined broadly by the formula v in which R, R1, R3 and R3 are alkyl radicals as'deflned above,'M is a monoor polyvalent metal, andxis the valence of M.

The effectiveness of our new slushing oils is due, we believe, to the particular chemical structure and properties of the dialkyl diphenol sulfide salts added thereto. Although we do not wish to be bound by any particular theoretical explanation it' appears fromthe evidence before us at present that the superior properties of our slush-- ing oils are due to a number of specific and interrelated factors contributed by the dialkyl diphenol sulfide salts acting in conjunction with the oil comprising the remainderof the compo- 'sition. "It will be observed from the structural formula given above-that the phenol hydrogen has been replaced'with a metal. The metal-surface to be protected from corrosion by the slushing oil and the metal radical, or radicals, of the dialkyl diphenolsulfide salt are believed to have an afilnity, or attraction, for each other and'when slushing oils containing such dialkyl diphenol sulfide metal salts are applied to a metal surface the dialkyl diphenol sulfide metal salt is believed to be very firmly attached to the metal surface it appears that the dialkyl diphenol sulfide metal salt is plated out on the metal surface ina continuous film one or more molecules in thickness.

1 The non-metallic portion of the dialkyl diphenol sulfide metal salt contains alkyl groups 2,sa4,o71 v ;sponding* 2,4-dialbl phenol with sulfur dichloride in solution in a suitable solvent such as carbon tetrachloride, ethylene chloride, trichlorethylene and the like. The sulfide forms readily with good yield andmetal saltscan be prepared therefrom by direct action of the metal hydroxide or metal alcoholate in the case of'strongly basic I metals, or by double decomposition of the alkali metal salt with an alcoholic salt solution of the desired metal. Single metal salts can be pre- I pared or mixed; metal salts by using a mixture of the different metal compounds. The barium salt of 2,4-dialkyl phenol sulfide is prepared for 1 example in the following manner:

of sufiicient length to be easily soluble in the oil portion of our improved slushing oil composi-' tion. These alkyl groups are held close to the metal surface to form a closely packed outer layer which, being chemically similar to the oil, promotes the formation of a second film, consisting of oil, over the metal surface. Since the alkyl groups of the dialkyl diphenol sulfide metal salt and the oil portion of the slushing oil are similar in character and are both' non-polar it will be seen that they are mutually soluble and will not be easily separated by water which is always present in a corrosive atmosphere. Accordingly the dialkyl diphenol sulfide metal salts cause a protecting oil film to be formed on the metal surface which is'not easily removed. f

The dialkyl diphenol metal salts themselves are not water-soluble and they are not removed by solvent action should the metal article be subjected to the washing action of large volumesof water. It is also pointed out that these compounds are hydrolyzed only with difilculty owing to the insolubility of the compounds and also to the fact that both ortho positions in each benzene nucleus are substituted andthe metal radical is thus protected from the action of water. Even if some hydrolysis should occur, as in the presence ;of carbonic acids, sulfurous acids and other dilute acids found in corrosive atmospheres, the metal radical which is split off as a result of the hydrolysis will, particularly in case of the alkaline earth metals, tend to neutralize the acid and prevent its action on metal surfaces.

The dialkyl diphenol sulfide metal salts are thus seen to have a double function in slushing oils in the prevention of corrosion.

In accordance with the foregoing principles the 30 parts of 2/4-diamyl phenol monosulfide is dissolved in a'mixture of about 50.parts of absolute alcohol and 50 parts of a petroleum naphtha containing about 70% aromatic hydrocarbons. 17.1 parts of'Ba(OH)z.8H2O is added with stirring and the mixture warmed to eflect solution and later to evaporate the water along with the solvents. Traces of the solvent are removed by warming in vacuo. The barium salt of the 2,4-diamyl phenol monosulfide is obtained as a viscous product which turns a dark, dull-colored green on exposure to the atmosphere. I

The efllciency of our new slushing oils may be demonstrated in an accelerated corrosion test which has been recognized in the art'as giving very accurate indications as to-the effectiveness of the slushing oil. A small quantity, 0.02% of our dialkyl diphenol sulfide metal salt, is added to a technical whiteoil and a strip of polished cold-rolled steel is placed therein. After allowing 10 minutes forthe dialkyl diphenol sulfide metal salt to plate out on the metal 1% of water is added to the oil and the mixture is stirred continuously throughout the test. Inthe absence of any inhibitor the polished metal strip will begin to show evidence of corrosion within about 30 minutes whereas with our inhibitors as herein described the polished steel strip maybe contacted with the oil and water mixture for periods 1 than 0.01% of the total weight ofthe slushing complex salts having a number of aryl sulfide groups may be formed, and such complex salts are also included within the scope of the invention. a v v The dialkyl diphenol sulfide metal salts may be We have found orepared by various methods. hat an excellent method is toreact the correfor most purposes.

oil to more than 10%. Ordinarily however 0.020.5% of the inhibitor will be found adequate Another advantage of our 2,4-dialkyl diphenol sulfide. metal salts is that we are enabled thereby to incorporate in mineral oils certain materials which are known to have good corrosion preventing properties but which cannot normally be used in slushing oils on account of their oilinsolubility. For example, calcium, barium, aluminum, zinc and magnesium stearates, palmitates and naphthenates, etc., are known who good film-forming materials havinganti-rusting properties but are difiicultly soluble in petroleum oils. Because of their solubility, however, in our dialkyl diphenol sulfide metal salts and the solubility of the latter class of materials in oils, it.'

is. possible to incorporate in slushing oils substantial amounts of these compounds, the presence of which markedly improves the corrosion resistance of the slushing oil.

Various fatty acids, drying oils, resins, metal oxides, solvents and other materials such, for example, as barium dialkyl dithiophosphates may also be added to our improved slushing oils when it is desired to modify them in other respects. I

In our copending application, Serial No. 383,167, filed March 31, 1941, now Patent No. 2,249,626, dated July 15, 1941, we claim a lubricating oil composition containing 2,4-dialkyl phenol sulfide metal salts in which the metal salt is added as a sludge dispersing agent. It will be understood of course that the lubricating oil composition as claimed therein is entirely distinct from the slushing oils of the present invention as set forth in the appended claims; the compositions themselves being not analogous and the dialkvl diphenol sulfide metal salts acting in a difl'erent way in the respective compositions. The slushing oils of the present invention are not to be regarded as lubricants since their purpose is not to lubricate but to protect metal surfaces from atmospheric corrosion.

What we claim is:

1. A slushing oil composition containing a major proportion of a mineral oil and DIM-% by weight of calcium 2,4-diamyl diphenol monosul- 3. A method of protecting metal surfaces from atmospheric corrosion which comprises applying thereto a slushing oil composition comprising a major proportion of a water-insoluble film-forming mineral oil having dissolved therein 0.1 to 10% of a metal salt of a 2,4-dialkyl diphenol sulfide in which each alkyl group contains at least 4 carbon atoms.

4. A method of protecting metal surfaces from atmospheric corrosion which comprises applying thereto a slushing oil composition comprising a major proportion of a mineral oil and 0.0110% of a 2,4-dialkyl diphenol sulfide metal salt having the following formula in which R, R1, R2 and R: are alkyl radicals having at least 4 carbon atoms, M is a metal and X is the valence of M. v

5. A method of protecting metal surfaces from atmospheric corrosion which comprises applying thereto a slushing oil composition containing a major proportion of a mineral oil and 0.01-10% by weight of calcium 2,4-diamyl diphenol monosulfide.

ELMER W. COOK. WILLIAM D. THOMAS, JR. 

